Introduction to Passive House is intended to be an easy-to-read introduction to why and how architects, policy makers and all those who procure works to new and existing buildings can collaborate in transforming the quality of our built environment, domestic and non-domestic, new-build and existing. The benefits of this transformation embrace occupants, users and the wider natural environment; now and for countless generations into the future. Small additional costs now will bring substantial benefits to people and national economies now, and these will accumulate into gigantic benefits for future generations. The steps we need to take are not difficult or expensive but the stakes and rewards could not be higher.